1. Field of the invention
The present invention relates to a printer for printing characters, symbols, and patterns etc., and more particularly to a drive circuit for a printing head adapted to have a structure which is to be mounted on the printer.
2. Description of the Prior Art
Printers are widely employed as output devices in various information processing apparatuses such as, for example, peripheral units of electronic computers, terminal equipment connected to telephone lines, and efforts have been made with respect to terminal equipment and peripheral units so as to miniaturize them, and reduce their weights as well as their power consumption with the developments of electronics. Likewise, a great deal of effort has been exerted on printers used as output devices. In particular, for printing heads used in such printers, various systems have been developed for practical use. For example, there are known printing heads for thermal printers each having micro heating elements, seven longitudinally and five transversely, provided on a ceramic substrate as well as another type of printing head for dot-wire printers including seven printing wires longitudinally and driven by an electromagnetic force. FIG. 1 illustrates a drive circuit for driving a dot printing head for use in such a prior art printer, and includes a control unit 1 consisting of a controller 2 including 2 microprocessors, etc., a drive circuit 3 connected to the controller 2 and including drive elements such as transistors, and a connector 4 connected to the drive circuit 3. The connector 4 is connected to a connector 7 provided on a carriage 6 via a connecting cord 5. The carriage 6 has the connector 7 and a printing head 8 connected to the connector 7. Furthermore, the printing head 8 will be described as the printing head for the dot-wire printer described above. Accordingly, printing wires arranged on the printing head 8 are selectively driven, while permitting the carriage 6 to be moved along a printing line, with the aid of the drive circuit 3 operated in accordance with an instruction issued from the controller 2 for allowing any character arranged in a 7.times.5 dot matrix to be printed. FIG. 2 shows a structure of the drive circuit 3 of the printing head monted on the printer, and includes a drive element 3b which is mounted by means of screws on a heat sink 3a used as a radiator; the heat sink 3a, the controller 2, and the connector 4 are mounted on a printed circuit board 1a which forms a prescribed electrical circuit. However, such a prior art circuit suffers from a drawback that since it has only a printing head, an object to be driven, mounted on the side of the carriage, a larger mounting space for the drive elements is required on the side of the control unit corresponding thereto. More particularly, printers needed for a higher printing quality must respectively have many printing wires. Accordingly, such a printer must include as many drive elements as those corresponding to the number of the printing wires and thus presents severe problems to be solved. In addition, a printing head using such dot wires requires more electrical power to be consumed in drive elements serving to drive loads, thereby requiring much more electric power. Therefore, one can not neglect heat radiation in the drive elements. It is thus necessary to reduce any influence of the heat on the controller, etc., provided on the same curcuit board by mounting heat sinks and cooling fans.